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Light reflecting within thin films can masquerade as molecular signals in perovskite solar materials

An infrared signal thought to reveal how molecules in perovskite solar materials respond to light-generated charges can arise largely from the way light travels through the thin film itself, a new theoretical study shows. Jun Nishida, assistant professor at the Institute for Molecular Science (IMS), Japan, found that light-generated charges alter how infrared light is reflected and transmitted within the film layers, producing sharp features that resemble changes in molecular vibrations even when the vibrations themselves are unaltered.

Published in The Journal of Chemical Physics and selected as an Editor’s Pick, the study names this mechanism carrier-induced photonic resonance (CIPR) and shows that it must be distinguished from genuine molecular responses when interpreting such measurements.

Barium titanate’s optical properties emerge more clearly after decades of widely varying measurements

A KAIST-led research team has characterized how light propagates through and is absorbed by barium titanate (BTO), a promising material for next-generation optical communication devices. By clarifying optical properties that had been difficult to determine because of the material’s complex internal structure, the study provides a foundation for designing these devices.

The research team led by professor Min Seok Jang of its School of Electrical Engineering had precisely characterized BTO’s refractive index and absorption properties across wavelengths ranging from the ultraviolet to the far-infrared. The study was conducted in collaboration with professor Harry A. Atwater’s team at the California Institute of Technology (Caltech), the Korea Research Institute of Standards and Science (KRISS) and U.S.-based J.A. Woollam Co. The work is published in ACS Photonics.

BTO’s refractive index changes when an electric field is applied. Its strong electro-optic response, known as the Pockels effect, makes it a promising material for optical modulators, which encode information from electrical signals onto light.

Atomic defects leave telltale optical fingerprints in quantum material

The tiny atomic defects so important for future quantum technologies can be difficult to spot. Fortunately, they leave behind some clues. The defects can alter how a material responds to light, producing a distinctive optical fingerprint that scientists can measure. The challenge is figuring out which fingerprints belong to which defects.

To that end, a University at Buffalo–led team has predicted the optical fingerprints of known atomic defects in hexagonal boron nitride (h-BN), a material with a honeycomb-like pattern of boron and nitrogen atoms. The team’s computer models simulated how different defects affect the intensity and polarization of the light produced when h-BN is hit with a laser.

Published in Nano Letters, these calculations could eventually help scientists distinguish between different types of defects in h-BN and determine which could be useful for emerging quantum technologies.

Quantum interference keeps two atoms bound despite enough energy to break apart

How can something remain intact when it should naturally break apart? This question has been addressed by researchers at RPTU. Their work has led to the experimental observation of an unusual quantum state in which two atoms remain bound together even though they possess enough energy to separate. The results have been published in the journal Nature Physics.

“What is remarkable is that the molecular state could decay from an energetic point of view, yet quantum interference suppresses this decay,” explains professor Artur Widera, head of the Individual Quantum Systems group at RPTU. “The wave nature of matter allows a state to remain bound even though we would normally expect it to decay.”

In simple terms, particles such as atoms do not behave solely like tiny objects. They also possess wavelike properties. When such waves overlap, they can either reinforce or cancel one another, a phenomenon physicists refer to as interference. As the new study demonstrates, it is precisely this effect that prevents two atoms from separating.

High-pressure setup unlocks detailed measurements of organized structures in turbulent flows

Turbulent flows are ubiquitous: they are found in clouds, in the ocean and even on other planets. Yet despite their chaotic nature, they also form large-scale structures that can be calculated and predicted. For example, while long streaks of clouds may appear orderly from the outside, their interiors are characterized by intense turbulence.

The high-pressure chamber at the Max Planck Institute for Dynamics and Self-Organization (MPI-DS), nicknamed the “submarine,” makes it possible to better understand the formation of these large-scale structures. Headed by research group leader Stephan Weiss and Director Eberhard Bodenschatz, the physicists have designed a special setup for such measurements. Their work is published in the Review of Scientific Instruments.

“The challenge is to generate flows with particularly strong turbulence, similar to those found in nature,” says Weiss. In their setup, the team uses a rectangular convection cell measuring 3.5 m long and 0.7 m high, whose temperature at the bottom and top can be regulated very precisely using heating and cooling plates. The experiments are conducted in a heavy gas (sulfur hexafluoride) at a pressure of up to 19 bar to replicate the large-scale turbulent flows found in nature on a smaller scale.

Accidental discovery enables room-temperature recrystallization of molybdenum

Researchers at the University of Rochester and Technion–Israel Institute of Technology accidentally discovered a new way to rearrange the internal structure of molybdenum—an extremely heat-resistant metal—at room temperature. Molybdenum is typically used to reinforce nuclear reactors, jet engine turbine blades and rocket nozzles because it doesn’t melt until it is heated to more than 2,600°C (4,712°F). Controlling its atomic structure at room temperature could open the door to more applications, including next-generation semiconductors.

The engineers found that pressing a fine diamond tip a few nanometers into molybdenum can reform the crystals inside molybdenum, giving the metal new properties. The results, published in the Proceedings of the National Academy of Sciences, took the researchers by surprise.

Water may play critical role in how our tissues stretch and spring back

Every time your heart beats, your lungs expand, or your skin stretches, a remarkable protein called elastin helps your body return to its original shape. But what exactly gives this protein its elasticity? For more than 50 years, scientists have debated whether elastin’s ability to stretch and recoil comes primarily from the protein’s own flexibility or from its interactions with surrounding water molecules.

Now, researchers at the University of Connecticut College of Engineering have uncovered new evidence suggesting that water plays a much larger role than previously understood. In a study published November 9 in Nature Communications, Anna Tarakanova, associate professor in the School of Mechanical, Aerospace, and Manufacturing Engineering, and postdoctoral researcher Metehan Çam used advanced computer simulations to investigate the molecular mechanisms behind elastin’s remarkable elasticity.

“Elastin is the body’s natural spring,” said Tarakanova. “It helps arteries expand and recoil with each heartbeat, allows the lungs to stretch and relax during breathing, and gives skin some of its ability to return to shape.”

Scientists turn protein-making errors in cancer cells into a targeted kill switch

Like every other cell in the human body, cancer cells also produce their own share of proteins for survival. During this production process, cells often encounter a glitch called ribosomal frameshifting. This exceptionally rare event occurs roughly once in every 100,000 translation events, when the ribosome, while reading genetic instructions to make a protein, shifts its reading position. A recent Nature study investigated whether this protein-building glitch in cancer cells can be turned into a targeted cancer therapy.

Ribosomes read mRNA in groups of three genetic letters, known as codons. To find out where this reading process goes wrong, the researchers developed high-throughput dual-luciferase reporter libraries containing randomized genetic sequences. This allowed them to systematically track instances where ribosomes slipped out of their usual reading frame.

The ribosome profiler pinpointed specific codon pairs, such as AGAACG, that frequently trigger ribosomes to slip backward by one letter (a −1 frameshift) in cancer cells. Noncancerous cells, however, read these sequences normally.

Upgraded microscope can now watch individual quantum particles in motion

Energy can be carried in a number of ways: by electrons, the particles that underpin all modern electronics, as well as by quasiparticles, the results of different particles interacting with one another at the quantum level. Columbia chemist Milan Delor has been watching these different forms of energy flow with an instrument called stroboSCAT, a unique microscope that uses strobe-like light pulses to capture particles and quasiparticles as they move through different materials.

The latest iteration of stroboSCAT, described in Nature Materials, can now resolve individual quantum energy carriers as they move through materials for the first time. It can also observe their interactions with greater precision than existing imaging techniques.

Electrons can easily be tracked using transport measurements that record electrical resistance. But such techniques cannot directly capture quasiparticles, like charge-neutral excitons or spin excitations. Delor first developed stroboSCAT as a postdoc working with Naomi Ginsberg at the University of California, Berkeley, in 2019. Over the years, he and his lab at Columbia have increased its temporal resolution to femtoseconds and its spatial resolution to just a few nanometers, and deployed it to detect electrons, excitons, phonons, magnons, ferrons, photons, polaritons and polarons in a variety of semiconductors and metals.

Your brain may map emotional concepts onto a hexagonal grid, new study suggests

Everyday life throws a whole range of emotional experiences our way, from exciting and relaxing moments to tense or gloomy encounters. Each experience is shaped by what’s present around us in the moment, the sensations our body is experiencing and our past experiences. This entire scene is set by the brain, which draws on these experiences of the past, organizing the information it gathers into mental maps that help us predict what might happen and respond appropriately to different situations.

In a recent study published in PLOS Biology, researchers investigated whether the human brain maps emotions using a coordinate system. They designed emotion-tracking experiments and behavioral tests in which participants watched changing facial expressions or read pairs of emotionally meaningful phrases, then judged changes in pleasantness or arousal. During these tests, researchers peeked into their brain activity using high-resolution functional MRI (fMRI).

The scans revealed a distinct sixfold (hexadirectional) symmetry in the ventromedial prefrontal cortex (vmPFC)—the brain’s emotion regulation, decision-making and self-control center—as participants tracked changes in emotion. The neural activity followed a geometric pattern, with brain patterns showing greater similarity when emotional paths aligned with the same 60° grid angles than when they did not.